I've run the Pertronix I and recomended coil in my T Bird without the resistor.for many years with no issues. Switched to the Pertronix II and recomended coil with no resistor several years back and no issues. Been running the Pertronix I in my 65 Mustang with no resistor and the recomended coil for a while with no Issues. Been running a Pertronix in my Two Cylinder John Deer with no problems for many years. Maybe I'm just lucky.

The gap across the button let the coil voltage rise higher. Usually trying to fire oil-fouled plugs. 

Just as a side point. An old friend of the family who has long since past, told me in the early days they would put a large button in the lead from the coil to the distributor to up the voltage and get a stronger spark. Possibly talking pre-war times.

I’ve run a Pertronix ll for 6+ years using their recommended coil. Prior to installing I called their tech line (I’m about 20 miles from them) to ask about using the stock resistor. The tech said either way would be fine other than the use of the resistor would not have the same voltage to the plug. I chose to use the resistor, the engine never misfires, plugs are always clean when I check. I’ll give up a little performance for reliability any time. Good luck

56 Vic, B'Ville 200 MPH Club Member, So Cal.

As a technical point, I hear people sometimes say a particular ignition coil "has an internal resistor". I'm not sure this is correct. I've never seen one. Maybe.

The coil winding DOES have a primary winding resistance, and it varies depending on the manufacturer and the intended application. The turns ratio between the primary and secondary windings is what determines the output voltage. It is a transformer, the ignition coil MUST be matched to whatever ignition type you're running, whether points or electronic ignition..

The dwell time is fixed with points, and the Ignitor I module. It is a compromise, because a fixed dwell isn't going to be optimal throughout the RPM range and a coil is going to run relatively hot at idle, is my understanding.

I bought an old Heathkit ignition analyzer after running into some ignition issues. Keep in mind the original OEM points design and materials that went in to distributor, cap, rotor and wiring were designed with 20,000 volt coils and a reduced primary voltage.

Now it is true that the voltage required to initiate a spark across the plug gap is only 10k or less at idle. In that sense "45,000 Volt Coil!!" is marketing hype. But it's also a factor of the input voltage into the primary winding, the turns ratio, and the spark plug gap. If you pull the ballast wire, run a .050" gap, it's going to put a lot of stress on the stock ignition components. It might seem to idle OK, but it may misfire under load or high speed and you'll see excessive voltage spikes on the firing line on the scope display.

What I found observing the ignition traces on a scope was that every piece of the ignition system has to be serviceable or stuff starts arcing to ground or crossfiring and weird stuff. Remember, they weren't designed for full time battery voltage.

If the spark plug gap is opened up - then the ignition coil output voltage will rise higher. This is generally a good thing, it means a hotter, longer, fatter spark. But if taken too far, then stuff starts burning up and misfiring and generally finding an easier path to ground.

There's one more air gap in the secondary ignition system that ALSO affects the output firing voltage and that is the air gap between the rotor tip and the distributor cap terminal. If you compare 1950s and 1960s rotors with later aftermarket or service replacements it is noticeably longer.

I had to sort through a few of them to find the right one, the part # didn't change but the part did. I think it may have been an emissions thing. These wide gap rotors seem to make the ignition coil run a fair bit hotter, because the average output is higher. That's my theory anyway. When I replaced the rotor the firing voltages settled down nicely on the scope, no more fireworks display around the engine bay.

Try to find a pre-emission era distributor rotor, and, keep the spark plug gap stock and the coil should run cooler. I've used the same Ignitor I module and a stock 30 amp generator for 20 years now. It needs a minimum of 1.5 ohms resistance in the primary circuit.

Take the time to pencil out the current flow (amperes) through the primary circuit under RUN conditions it will start to make sense why, and what, ignition coil & resistor combinations and combinations are acceptable for any given Ignition. Points type were limited to about 3 amperes. The Ignitor I will tolerate about 8 amperes. This is while the engine is running - a V8 coil has about a 66% duty cycle as it were. This is also why leaving the key on in RUN without the engine running will start roasting points & ignition coil, the current flow quickly exceeds the normal 3 to 4 amps.

Ford D
I was using the Flamethrower 1 oil filled for about a year with no issues. Great performance. When it failed I replaced with epoxy filled because I noticed little drops of oil on the Valve cover. The coil sits horizontally.
None of the Epoxy lasted very long with exact same hook-up (no external resistor)
Ideally I want to use a high powered coil without a resistor to get the best performance.

Any advantage to running Pertronix II - can I then use a coil without external resistor?

As stated above, a 1.5 ohm coil may be what you need with Pertronix 1.  Even if you were to install Pertronix 2, the 1.5 ohm coil will run cooler with out an external resistor.  It is very advantageous to NOT use an external resistor in favor of a hotter spark. I did some crude testing with a distributor machine years ago with ignition components wired as would be in the vehicle. The difference is quite noticeable with out the resistor. Like, could draw about twice as long of an arc, the arc is much more intense, makes more noise, and ozone becomes very noticeable.  Also, because the rise time is quicker, a longer spark duration can be measured on an oscilloscope. So, yes, it's very beneficial to eliminate the resistor.  Do you know if your coil is oil filled are epoxy filled?  There is the possibility that an oil filled coil operated horizontally can leave part of the internal coil core not covered with heat conducting oil. For sure, there will be an air space along the length of the horizontal surface inside the canister.  Just some food for thought. For that reason, I always use an epoxy filled coil just to error on the cautious side.  For several years I ran Pertronix2 with no resistor and 1.5 ohm coil with no issues. Hope this helps, JEFF...........


64F100 57FAIRLANE500

Florida Phil are you using the Flame Thrower with External resistor?
The Flamethrower I had originally lasted about 1 year without external resistor. Great performance.
I then replaced with 2 more and they failed quickly.
If I use flamethrower with external resistor its fine but defeats purpose -
The MSD Blaster II I am currently using has been in there for 2 years using external resistor performance is good.

In short I would like to use a coil without resistor for better performance.

My 292 has a stock 1957 Ford distributor with a Pertronix I unit.  My coil is a 1.5 Ohm Pertronix Flame Thrower coil.  My coil does not run hot.  It has been in my car for over a year without any issues.  I did have an intermittent problem with the overdrive kick down switch.  I removed the wire from the switch to the coil and it has worked fine since then.

I have had several conversations with the Pertronix tech. Too low resistance (combination of coil and ballast resistance) to the Pertronix will burn the Ignitor up. He said more resistance is OK, but performance "might" suffer at higher RPM. Also, voltage rises in the coil until the spark can jump to a ground. If you have good wires and other ignition parts, reasonable (not super high) compression, and a normal gap on the plugs, the spark will never rise to the advertised voltages on the high voltage coil, usually around 15,000-20,000 volts. The OP didn't say how many Flamethrower coils have failed. If only one, maybe it was a faulty part.